Telephone apparatus



E. C. WENTE TELEPHONE APPARATUS Filed Oct. 9, 1922 N E i E FrequencyWye/775% f'flwa/ d C. Wen/i2 I Fatented July 13, 1926.

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EDWARD C. WENTE, OF PORT WASHINGTON, NEW YORK, ASSIGNOR '10 WESTERN IELECTRIC OOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION 015new YonK.

TELEPHONE APPARATUS.

Application filed October 9, 1922. Serial No. 593,203.

An object of the invention is to provide an efficient and inexpensiveair-damping means which may be readily applied to standard types ofreceivers.

In accordance with the general features of this invention use is made ofa perforated plate of suitable material and thickness located adjacentto the receiver diaphragm for the purpose of damping the resonanceeffect of the receiver diaphragm. Although shown in the drawing aslocated upon the outer face of the diaphragm, the invention contemplatesthe use of this damping plate upon either side of the diaphragm. r

When a diaphragm is separated a-short damping and elastic constants areeffective- 1y increased. The magnitude of'these effects for plateshaving various perforations and grooves are well known. However,previous arrangements providing airdamping for receivers andtransmitters, require special and expensive structures, whereas theresent invention provides means which may be easily applied to anystandard type of r ceiver, and by its use, the response frequencycharacteristic is greatly improved without appreciable sacrifice inefficiency.

Fig. 1 is a'sectional view showing an application of the invention to astandard type F receiver.

Fig. 2 is a plan view of the damping plate.

Fig. 3 shows characteristic damping curves of receivers with and withoutdamping means.

The ordinary type of magnetic receiver diaphragm 4 hasan initialdisplacement owing to the magnetic pull of the magnet 5. For the sake ofclearness, this displacement is shown somewhat exaggerated. A plate r 6,preferably of non-magnetic material, is

superimposed upon the concave side of diaphragm l, and is held inrelation therewith y means of the usual receiver cap 8 to pro- -vide achamber between the plate 6 and the diaphragm 41 for a film of air.Plate 6 is preferablyof a thickness such that its resonance frequency isconsiderably higher than that of the diaphragm i, and is perforated withone or more holes 9 through distance from a plane parallel plate, bothits which air passes back and forth as the diaphragm 4 vibrates. Onaccount of its vis oosity the air will flow lessfreely through the holes9 as the frequency of the vibration of the diaphragm is increased. Itis, therefore. evident that a perfectly rigid plate would reduce theefficiency of the receiver at the high frequencies. If, however, plate 6has a resonance frequency somewhat higher than that of the diaphragm, itwill vibrate with the diaphragm at the higher frequencies, while at thelower frequencies air will flow freely through the openings. At thehigher frequencies, the stiffness factor of the vibrating system is thusgreater than that of the diaphragm alone, and consequently within acertain region the amplitude of motion of the diaphragm and plate meantcombined will be greater than that of the diaphragm without the dampingplate, the plate and the diaphragm forming a coupled system, thecoupling being very loose at low frequencies, but becoming closer andcloser as the frequency is increased. The effect of the plate on theefiiciency of the receiver is, therefore, to alter the response belowthe natural frequency but little, dampen out the free vibrations, cutdown the response within the regions of resonance, and increase theresponse within a certain region at the higher frequencies.

In Fig. 3, the curve 10 represents the frequency characteristic of anon-damped diaphragm in a commercial type of telephone receiver, and thecurve 11, represents the fre-v quency characteristic of the samereceiver stantially different frequency of vibration superimposedthereon and coupled thereto by a film of air such that the couplinggreatly increases at the higher speech and music frequencies. I

in a telephone receiver, a diaphragm, and a perforated plate ofnon-magneticmateriai superimposed upon said diaphragm,

said diaphragm and plate being in contact attheir peripheries andseparated at their centers by a him of air sutliciently thin to produceappreciable air damping of the'diaphragm at speech and musicfrequencies.

3. In telephone receiver, a diaphragm, a perforated platesecured insuperimposed relation thereon to form between the diaphragm and plate achamber for an air film which with the diaphragm and perforated plateconstitutes a coupled vibrating system which is very loose at lowfrequencies in the speech and music frequency range but becomes closerand closer as the frequency is increased Within the limits the speechand music frequency range.

4. Eu telephone receiver, diaphragm, a perforated plate of nonmagneticmaterial superimposed upon one side of said diaphragm, magnetic means onthe other side of said diaphragm to give it an initial displacementWhereby a chamber for an air film is termed between the center portionsof said diaphragm and plate, the dimensions of the said film and therelative size of the perforations in'the said plate being such as toproduce appreciable air damping within the speech and music frequencyrange;

5. A method of controlling resonance eftects in a telephone receiverdiaphragm which consists in providing a perforated diaphragm juxtaposedin such a relation with the receiver diaphragm as to be loosely coupledtherewith at low frequencies and more closely coupled as the frequencyincreases within the speech and music frequency range.

6. in a telephone-receiver, vibratory diaphragm, means to apply amagnetic force on one side of said diaphragm, an air film means and aperforated plate superposed on the other side of said diaphragm andhaving a higher resonant frequency than that of the said diaphragmalone, said diaphragm and said perforated plate being coupled by thesaid film of air, the relative dimensions of the parts being such thatthe coupling greatly increases at the higher speech and music frequency.

i. in a telephone receiver a diaphragm having a predetermined frequencyof vibrat1on, damping means comprising a perforated plate ofsubstantially ditierent frequency placed over the diaphragm so that whenthe diaphragm is in its unconstrained condition, said diapragm plate arein contact over their entire surface, and magnetic'means for holdingsaid diaphragm and plate in spaced relation at their centers.

8. A method of controlling the acoustics of a telephone receiver whichconsists of superimposing upon the receiver diaphragm plate a perforatedplate of non-magnetic material and of a ditl'erent frequency from thatof the receiver diaphragm, and applying magnetic force to one plate toproduce an air chamber between said plates.

9. A method of controlling the acoustics of a telephone receiver whichconsists in positioning in front of said receiver diaphragm plate asecondary perforated diaphragm plate of a non-magnetic material having afrequency substantially diifercnt from that of the receiver diaphragm,and applying magnetic force to one plate to produce an air chamberbetween said plates.

In Witness whereof, I hereunto subscribe my name this 3rd day or OctoberA. 1'),

EDVJARD C.

